The bicarbonate-containing artificial perfusing fluid is one of the dialyzing fluids for perfusing artificial kidney systems and generally comprises a concentrated aqueous solution of various electrolytes necessary for hemodialysis (composition A) and a concentrated aqueous solution of sodium bicarbonate powder alone or in combination of part of the above-mentioned electrolytes (e.g. NaCl, CH.sub.3 COONa) (composition B). These compositions are placed in the respective tanks of an artificial kidney system for bicarbonate dialysis and, at the time of use, they are diluted with water and mixed together to give a dialyzing fluid. Such dialyzing fluid, which contains sodium bicarbonate (as composition B) originally known to be a factor directly adjusting the body fluid pH and hence physiologically adequate, efficiently and rapidly improves the acid-base balance in metabolic acidosis, respiratory alkalosis and the like, does not provoke indefinite complaints, such as hypotension and nausea, during dialysis, and can accomplish rapid dehydration. Therefore, said fluid is much expected to be effective and safe in the treatment of hyperpotassemia, hypocalcemia, hyperphosphoremia and hyperaceta, for instance, and especially in large-area short-time dialysis.
However, the above-mentioned sodium bicarbonate is low in solubility and unstable against acid pH and heat. Accordingly, it has the fatal disadvantage that, in preparing dialyzing fluids by admixing it with composition A and during storage of said fluids, it generates carbon dioxide gas and thereby causes increase of pH and decrease of carbon dioxide gas pressure, whereby calcium and magnesium in composition A precipitate out in the form of carbonate. Therefore, in preparing the above-mentioned bicarbonate-containing dialyzing fluids, the prior art used the technique of introducing carbon dioxide gas into the mixing tank (reaction vessel) to thereby compensate the loss of carbon dioxide gas due to escape and thus maintain the pH of the dialyzing fluids at or around the neutral pH or the technique of adding an appropriate amount of a mineral acid or organic acid to the above reaction vessel or composition A to thereby adjust the pH. However, these procedures themselves are rather complicated or troublesome and, in addition, highly precise concentration and pH control is required. Moreover, the above composition A itself is a concentrated solution, so that its storage stability cannot be secured, namely pH changes with the lapse of time, for example during storage, are unavoidable. The large volume and weight of such solution are its further disadvantages in its handling, such as transportation.
It is an object of the present invention to provide a method of producing a uniform-quality powder-form composition A for preparing bicarbonate-containing dialyzing fluids, which can be produced in an easy manner and on a commercial scale and in which necessary electrolyte ions are in a very uniformly mixed state without substantial variation in composition, and thereby solve not only the problems hitherto encountered in preparing bicarbonate-containing dialyzing fluids but also the stability and handling problems.